Phased Array Antenna Calibration via Built-In Test Probe
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Solution Overview
Problem
Existing phased array antennas face challenges in achieving precise calibration and maintaining accuracy across varying frequencies and temperatures due to mechanical and electrical tolerances, especially at microwave frequencies, making it impractical to fabricate antennas with the required process control for optimal performance.
Innovation Solution
A built-in-test (BIT) system using a calibration probe and a beamsteering computer to calculate revised phase and amplitude parameters, which includes a pseudorandom noise generator, power divider, programmable delay circuit, and detection circuit to calibrate individual antenna elements quickly and accurately, utilizing a broadband signal and periodic calibration to account for frequency and temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional near-field calibration methods are used to measure gain and phase characteristics of each element, then calibration accuracy can be achieved, but the process becomes time-consuming and is only valid at the specific frequency and ambient temperature where calibration was performed
Solution Approach 1:
The patent implements preliminary action by pre-calculating and storing compensation values for gain and phase errors across multiple frequencies and temperatures in lookup tables. During operation, the system simply retrieves the appropriate compensation values based on current operating conditions, eliminating the need for time-consuming real-time measurements while maintaining high calibration accuracy.
Solution Approach 2:
The system dynamically adapts to changing operating conditions by selecting appropriate calibration data from lookup tables based on current frequency and temperature. The beamsteering computer dynamically adjusts compensation parameters in real-time based on operational feedback, allowing the system to maintain accuracy across varying conditions without repeated calibration measurements.
2Manufacturing precision
If mechanical and electrical tolerances are tightened to achieve acceptable performance at microwave frequencies, then pointing accuracy improves, but fabrication becomes impractical due to the complexity and cost of achieving such precision
Solution Approach 1:
The patent changes the approach from controlling physical dimensions during fabrication to controlling electrical parameters (phase and amplitude) through software-based beamforming and compensation algorithms. This allows the system to achieve high pointing accuracy through digital signal processing rather than through difficult mechanical precision, making fabrication practical while maintaining performance.
Solution Approach 2:
The system replaces mechanical precision requirements with electronic and software-based solutions. Instead of relying on mechanically precise element positioning and fabrication tolerances, the patent uses electronic phase shifters, amplifiers, and digital signal processing to achieve the desired beamforming accuracy, thereby eliminating the need for impractically tight manufacturing tolerances.
3Reliability
If complex prior art designs with improved ASIC or monolithic microwave integrated circuit with coupling are used, then calibration capability is enhanced, but device complexity increases significantly
Solution Approach 1:
The patent implements a universal calibration and beamforming system where a single beamsteering computer performs multiple functions: it controls phase shifters, manages amplitude adjustment, executes calibration algorithms, and adapts to different operating conditions. This multi-functional approach replaces multiple specialized complex circuits with a single programmable system, reducing overall device complexity while enhancing calibration capability.
Solution Approach 2:
The system performs self-calibration and self-diagnosis through the beamsteering computer, which automatically measures and compensates for element variations without requiring external complex calibration equipment. The system uses its own resources (signal generators, detectors, and processors) to calibrate itself, eliminating the need for separate complex calibration subsystems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system enables rapid and accurate health analysis and calibration of phased array antennas, maintaining desired beam profiles and overcoming element failures, while being inexpensive and easily integratable into existing designs without affecting performance.
Implementation Method 1
a calibration probe, preferably a monopole radiator that is able to transmit or receive a modulated signal supplied from an input source
Implementation Method 2
detecting the signal output from the selected element and comparing the detected signal with the applied signal
Data Source
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Figure 3A
AI summary
A method and apparatus is disclosed that is capable of verifying on site the health, calibration and integrity of individual phased array modules of a phased array antenna system and, in certain cases, enabling the phased array antenna system to overcome element failures by use of a beam-steering computer (i.e. beamsteering). The present disclosure provides a test probe or RF radiator in or adjacent the antenna array for supplying and receiving test and calibration signals.